The thoughts and experiences of a man who enjoys challenging arts, unplanned wanderings and intelligent conversations.

10 October 2009

Not understanding data very well at all

I went on the training course for school governors on interpreting data hoping to learn something but with the concern that it might simply be a rehash of arguments I have had with the Local Authority at governors' meeting.

In the event my hope were dashed and it proved to be a pointless evening. I'll try and explain why.

The course focused entirely on the analysis of certain data sets around pupil performance. But to use data properly you have to understand how it has been collected and presented.

There are many problems associated with testing children's performance, including the difficulty in setting tests that are consistent in what they measure (e.g. is this year's test set the same way as last year's?), difficulties in setting questions that are fair to all groups (e.g. asking our children to describe a day on the beach when most have never been to one), subjectivity in marking (e.g. range of vocabulary), accuracy in marking (each year thousands of papers are challenged by schools and sent back to remarking) and variations in performance caused by a pupil's emotional and physical state at the time of the test.

These sorts of issues should be familiar to anybody who has ever done any sort of scientific experiment where you look at the possible causes of error and try and find ways around them. The most obvious approach here is to take several readings and use an average.

The testing of children makes no attempt to correct for errors and so is implicitly suspect and what nobody can tell me is how suspect. Without this basic understanding of how the data has been collected, any further analysis is meaningless.

Another worry was that one of the presenters of the course did not seem to understand the basic principle that a half of schools will always be below average or that while a large number of children are tested overall in our, fairly typical, school is it only around 55 children which is not a statistically significant sample size.

To end a bad evening on a bad note, I was given this certificate of attendance which is now filed alongside my certificate for the 25m crawl (failed) in recycled paper heaven.